The present invention is applicable to butterfly valves and the like such for example as disclosed in U.S. Pat. No. 3,376,014-Buckley et al, U.S. Pat. No. 3,447,780-Hobson, Jr. and U.S. Pat. No. 3,837,620-Malloy et al.
In some butterfly valve constructions it is impractical due to size and other manufacturing considerations to have the valve closure member or disc fixed to the shaft. When the valve closure member or disc is not fixed to the shaft, the full weight of the disc exerts a downward force when mounted in other than a horizontal position. This force frequently brings about excessive wear and increased friction between the disc and the valve seat or liner material, as well as causing an imbalance in the sealing force around the disc. As the valve increases in size, this condition becomes more acute and is particularly accentuated where softer sealing materials are used.
When the disc is supported on the main shaft or is supported at its lower end by a removable stud shaft, the axial position of the disc relative to the valve seat may be adjusted by means of an externally accessible adjusting screw operable to apply a force to the end of the supporting shaft. Thus movement of the shaft will in turn cause movement of the disc which is supported on the shaft. Examples of arrangements of this type are disclosed in U.S. Pat. No. 3,314,642 - Kautz et al, U.S. Pat. No. 3,633,872 - Wright. Other patents showing the use of a plug for supporting the shaft are U.S. Pat. No. 3,497,180 - Ryey, U.S. Pat. No. 3,539,148 - Boos, Jr. and U.S. Pat. No. 3,703,910 - Smith.